Indocyanine Green permits recording of the indicator-dilution curves for both diagnostic and research purposes independently of fluctuations in oxygen saturation. In the performance of dye dilution curves, a known amount of dye is usually injected as a single bolus as rapidly as possible via a cardiac catheter into selected sites in the vascular system. A recording instrument (oximeter or densitometer) is attached to a needle or catheter for sampling of the dye-blood mixture from a systematic arterial sampling site.
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Under sterile conditions, the Indocyanine Green for Injection USP powder should be dissolved with Sterile Water for Injection, USP, and the solution used within 6 hours after it is prepared. If a precipitate is present, discard the solution. The amount of solvent to be used can be calculated from the dosage form which follows. It is recommended that the syringe used for injection of the dye be rinsed with this diluent. Saline is used in all other parts of the catheterization procedure.
This matter of rinsing the dye syringe with distilled water may not be critical, since it is known that an amount of sodium chloride sufficient to make an isotonic solution may be added to dye that has first been dissolved in distilled water. This procedure has been used for constant-rate injection techniques without precipitation of the dye.
The usual doses of Indocyanine Green which have been used for dilution curves are as follows:
Adults&#;5 mg
Children&#;2.5 mg
Infants&#;1.25 mg
These doses of the dye are usually injected in a 1-mL volume. An average of five dilution curves is required in the performance of a diagnostic cardiac catheterization. The total dose of dye injected should be kept below 2 mg/kg.
To quantitate the dilution curves, standard dilutions of Indocyanine Green in whole blood are made as follows: It is strongly recommended that the same dye that was used for the injections be used in the preparation of these standard dilutions. The most concentrated dye solution is made by accurately diluting 1 mL of the 5-mg/mL dye with 7 mL of distilled water. This concentration is then successively halved by diluting 4 mL of the previous concentration with 4 mL of distilled water. (If a 2.5 mg/mL concentration was used for the dilution curves, 1 mL of the 2.5 mg/mL dye is added to 3 mL of distilled water to make the most concentrated "standard" solution. This concentration is then successively halved by diluting 2 mL of the previous concentration with 2 mL of distilled water.) Then 0.2-mL portions (accurately measured from a calibrated syringe) of these dye solutions are added to 5-mL aliquots of the subject's blood, giving final concentrations of the dye in blood beginning with 24 mg/liter, approximately (actual concentration depends on the exact volume of dye added). This concentration is, of course, successively halved in the succeeding aliquots of the subject's blood. These aliquots of blood containing known amounts of dye, as well as a blank sample to which 0.2 mL of saline containing no dye has been added, are then passed through the detecting instrument and a calibration curve is constructed from the deflections recorded.
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The use of indocyanine green angiography (ICG-A) to assess tissue perfusion has been described in gastrointestinal surgery to assess bowel perfusion to guide resection or anastomosis as well as in reconstructive procedures to predict skin and soft tissue viability. We present a novel use of this technology in which the Stryker SPY-PHI system (a handheld indocyanine green fluorescence imaging system) was utilized to aid in tissue resection boundaries based on perfusion in a patient with acute necrotizing fasciitis.
A 68-year-old, morbidly obese female presented with several days of worsening perineal and left gluteal pain. Examination of her left labia majora and left gluteal fold was consistent with a necrotizing soft tissue infection. Computed tomography confirmed the diagnosis, demonstrating significant subcutaneous emphysema and abscess formation. She was taken emergently to the operating room for primary debridement. On postoperative day two she returned to the OR for wound washout and possible re-debridement. Grossly non-viable tissue was first excised; then fluorescence perfusion assessment was utilized to assess for non-viable and poorly perfused tissue that would have otherwise not been debrided based on visual examination. The patient subsequently recovered quickly without the need for further debridement. She was discharged with local wound care.
Given that the surgical tenet for necrotizing soft tissue infections is serial debridement, the use of fluorescence perfusion assessment as an adjunct for intraoperative debridement decisions may potentially minimize the need for repeated debridement, thus achieving quicker source control. To our knowledge, this is the first documented use of this technology in the management of necrotizing soft tissue infections.
indocyanine green angiography; necrotizing fasciitis; NSTI
Necrotizing soft tissue infections (NSTI) are life-threatening conditions that require prompt surgical intervention. Due to the aggressive nature of NSTIs, delay in diagnosis and treatment increases morbidity and mortality, and clinical diagnosis based on history, physical examination, and high clinical suspicion remain crucial.1&#;3 In addition to antibiotics and resuscitation, the mainstay of NSTI management is early surgical debridement.4 This typically requires multiple returns to the operating room to debride grossly infected and non-viable tissue until complete source control is obtained.
The use of indocyanine green angiography (ICG-A) to assess tissue perfusion has been well-described in bowel surgery to evaluate bowel perfusion for resection or before anastomosis, but it is also utilized in reconstructive procedures to predict skin and soft tissue viability.5&#;7 Several plastic surgery reports have shown that the addition of ICG-A with clinical examination was a useful and safe technique in monitoring free flap compromise both intraoperatively and postoperatively, leading to improved flap success rates.8 After a review of the literature, this technology has not been utilized in the setting of NSTI debridement. We present a case of necrotizing fasciitis in which the Stryker SPY-PHI system (a handheld indocyanine green fluorescence imaging system) was utilized to aid in tissue resection boundaries based on perfusion.
A 68-year-old, morbidly obese female who presented to the emergency department with several days of worsening perineal and left gluteal pain while visiting from outside the country. Examination of her left labia majora and left gluteal fold was consistent with a necrotizing soft tissue infection. Computed tomography (CT) demonstrated significant subcutaneous emphysema and abscess formation, consistent with necrotizing fasciitis (Figure 1). Laboratory values were consistent with an elevated WBC of , hyponatremia, and lactic acidosis. Given these findings, she was taken emergently to the operating room for primary debridement.
Figure 1. CT Imaging Revealed Significant Inflammation and Gas in Subcutaneous Tissues, Consistent With Necrotizing Fasciitis. Published with Permission
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